Process-diagnostic patterns of chlorobiphenyl congeners in two radiochronologically characterized sediment cores from the northern Baffin Bay

Polychlorinated biphenyl (PCB) patterns were interpreted in two radioisotop ically constrained sediment cores from the Arctic ocean in order to seek cl ues about their large-scale environmental fates. Low but clearly measurable fluxes of individual PCB congeners were observed in deeper layer sediments , corresponding to the past 170 years, in a single dated core from the Baff in Bay shelf. Fluxes of the dominant individual congeners in the surface se diments were 20-100 mug m(-2) d(-1). Combining these data with the sediment data from the Arctic Monitoring and Assessment Program, it appears that th e PCB distribution in Arctic surface sediments is governed by the organic c arbon (OC) content of the sediments. The historical development of the PCB congener fingerprint suggests that the modern sediments are enriched in med ium-chlorinated congeners, implying that there are at least two significant , but distinctly different, sink processes acting on the PCB pool. The rela tive abundance of light-to-heavy congeners, in mid-shelf marine sediments o f similar ages, between 40 degreesN and 76 degreesN latitude suggests a nor thward dilution of PCBs which is stronger attenuated for heavier congeners, consistent with a temperature-driven global fractionation process. The sig nificant presence of PCB in historical archives pre-dating the organochlori ne society, as observed in this and several previous studies, awaits a full er explanation. (C) 2001 Elsevier Science Ltd. All rights reserved.